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Secondary organic aerosol (SOA) can affect the atmospheric radiation balance through absorbing light at shorter visible and UV wavelengths. However, the composition and optical properties of light-absorbing SOA is poorly understood. In this work, SOA filter samples were collected during individual chamber experiments conducted with three biogenic and eight aromatic volatile organic compound (VOC) precursors in the presence of NO X and H 2 O 2 . Compared with the SOA generated using the aromatic precursors, biogenic SOA generally exhibits negligible light absorption above 350 nm; the aromatic SOA generated in the presence of NO X shows stronger light absorption than that generated with H 2 O 2 . Fifteen nitroaromatic compound (NAC) chemical formulas were identified and quantified in SOA samples. Their contributions to the light absorption of sample extracts were also estimated. On average, the m-cresol/NO X SOA sample has the highest mass contribution from NACs (10.4 ± 6.74%, w/w), followed by naphthalene/NO X (6.41 ± 2.08%) and benzene/NO X (5.81 ± 3.82%) SOA. The average contributions of NACs to total light absorption were at least two times greater than their average mass contributions at 365 and 400 nm, revealing the potential use of chromophoric NACs as brown carbon (BrC) tracers in source apportionment and air quality modeling studies.

Polar organic compounds and elements were quantified in PM(10) aerosols collected in urban and rural areas of Baoji, an inland city of China, during winter and spring 2008. Concentrations of biomass burning markers and high molecular weight n-alkanoic acids (HMW, >C(22:0)) were heavily increased in winter. In contrast, sugars presented in higher levels in the spring, among which sucrose was the most abundant with an average of 219ngm(-3) in winter and 473ngm(-3) in spring respectively. This suggests enhanced biotic activity in the warm season, whereas no obvious trend was observed for sugar alcohols, concentrations of the three sugar alcohols in spring were only 0.94-2.3 times as those in winter, indicating a second pathway of their formation other than fungal spores in cold season. Major crustal elements (i.e., Fe, K, Mn and Ti) in PM(10) aerosols were also observed in larger concentrations in spring samples than those in winter due to an enhancement of coarse particles from soil minerals. By using principal component analysis (PCA) and positive matrix factorization (PMF), sources and their contributions to the PM components were also investigated in this study. Four factors were extracted with both models, and the sources represented by different factors were based on the highest loaded marker species as follows: factor 1, soil and road dust (Fe, Sr and Ti); factor 2, biomass burning (levoglucosan, galactosan and syringic acid); factor 3, microbial emissions (fructose and sucrose); and factor 4, fossil fuel combustion and fungal spores influence (Pb, Zn, arabitol and mannitol). The high correlation between PM(10) and factor 1 suggested that PM(10) pollution in Baoji was dominated by soil and dust re-suspension., (Copyright © 2010 Elsevier B.V. All rights reserved.)

In this study, collocated filter samples of particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) from northern Nanjing were extracted using water and methanol, followed by analysis of light absorption. A backup quartz filter was used to correct sampling artifacts caused by adsorption of gaseous organics. The collocated precision of light‐absorbing properties of water‐soluble organic carbon (WSOC) and methanol‐extractable organic carbon (MEOC) were parameterized using correlation coefficient (r), coefficient of divergence (COD), and average relative percent difference (ARPD, %). In general, the light absorption of WSOC and MEOC showed good agreement (r > 0.80, COD < 0.20) between collocated samples. Performing artifact correction is necessary and will increase the heterogeneity between collocated measurements. The duplicate‐derived ARPD values of MEOC absorption were more than 60% higher than those of WSOC absorption. Then, it would be inappropriate to assume a uniform uncertainty fraction (e.g., ∼10%) for WSOC and MEOC absorption in future studies on their climate effects and source apportionment. To apportion artifact‐corrected absorption of aerosol extracts to specific emission sources or formation pathways, positive matrix factorization was performed by using concentration data of selected bulk species and organic molecular markers. Among the nine identified factor/sources, the biomass burning factor had the highest average contributions to the absorption of both WSOC (31.6%) and MEOC (48.0%), followed by dust resuspension and coal combustion factors. Unlike combustion‐related primary emissions, the factors containing influences from atmospheric processing (e.g., secondary nitrate) contributed more fractions of WSOC absorption than MEOC absorption. Key Points: Collocated measurements provide an approach to estimate uncertainties in light‐absorbing properties of solvent‐extractable organic carbonIgnoring the adsorption of gaseous organics onto filter medium will lead to significant overestimation of brown carbon absorptionAerosol sources influenced by aging processes contributed more fractions of aqueous extracts absorption than methanol extracts absorption [ABSTRACT FROM AUTHOR]

BSTRACT Primary (i.e. sugars and sugar-alcohols) and secondary (i.e. carboxylic acids) water-soluble organic compounds (WSOCs) in size-segregated aerosols from the urban and mountain atmosphere of China and from the marine atmosphere in the outflow region of East Asia were characterized on a molecular level. Levoglucosan is the most abundant compound among the quantified WSOCs in the urban and mountain atmosphere, whose concentration at the urban site was 1-2 orders of magnitude higher than that at the mountain and marine sites. In contrast, malic, succinic and phthalic acids were dominant among the measured WSOCs at the marine site. In the urban air, sugars except levoglucosan gave a bimodal size distribution with a large peak in fine range (<2.1 μm) and a small peak in coarse range (≥2.1 μm) during winter, being opposite to those in spring. In contrast, these WSOCs at the mountain and marine sites dominated in the coarse range but diminished and even disappeared in the fine range. Geometric mean diameters (GMDs) of the measured WSOCs in the fine mode at the urban site were larger in winter than in spring. Levoglucosan and carboxylic acids except for azelaic and benzoic acids showed a larger GMD in the coarse mode at the marine site probably due to an increased hygroscopic growth. [ABSTRACT FROM AUTHOR]

Abstract: Polar organic compounds and elements were quantified in PM10 aerosols collected in urban and rural areas of Baoji, an inland city of China, during winter and spring 2008. Concentrations of biomass burning markers and high molecular weight n-alkanoic acids (HMW, >C22:0) were heavily increased in winter. In contrast, sugars presented in higher levels in the spring, among which sucrose was the most abundant with an average of 219ngm−3 in winter and 473ngm−3 in spring respectively. This suggests enhanced biotic activity in the warm season, whereas no obvious trend was observed for sugar alcohols, concentrations of the three sugar alcohols in spring were only 0.94–2.3 times as those in winter, indicating a second pathway of their formation other than fungal spores in cold season. Major crustal elements (i.e., Fe, K, Mn and Ti) in PM10 aerosols were also observed in larger concentrations in spring samples than those in winter due to an enhancement of coarse particles from soil minerals. By using principal component analysis (PCA) and positive matrix factorization (PMF), sources and their contributions to the PM components were also investigated in this study. Four factors were extracted with both models, and the sources represented by different factors were based on the highest loaded marker species as follows: factor 1, soil and road dust (Fe, Sr and Ti); factor 2, biomass burning (levoglucosan, galactosan and syringic acid); factor 3, microbial emissions (fructose and sucrose); and factor 4, fossil fuel combustion and fungal spores influence (Pb, Zn, arabitol and mannitol). The high correlation between PM10 and factor 1 suggested that PM10 pollution in Baoji was dominated by soil and dust re-suspension. [Copyright &y& Elsevier]

Abstract: Foliar uptake of airborne lead is one of the pathways for Pb accumulation in plant organs. However, the approximate contributions of airborne Pb to plant organs are still unclear. In the present study, aerosols (nine-stage size-segregated aerosols and total suspended particulates), a wild plant species (Aster subulatus) and the corresponding soils were collected and Pb contents and isotopic ratios in these samples were analyzed. Average concentration of Pb was 96.5±63.5ngm−3 in total suspended particulates (TSP) and 20.4±5.5ngm−3 in the fine fractions of size-segregated aerosols (SSA) (<2.1μm), higher than that in the coarser fractions (>2.1μm) (6.38±3.71ngm−3). Enrichment factors show that aerosols and soils suffered from anthropogenic inputs and the fine fractions of the size-segregated aerosols enriched more Pb than the coarse fractions. The order of Pb contents in A. subulatus was roots>leaves>stems. The linear relationship of Pb isotope ratios (206Pb/207Pb and 208Pb/206Pb) among soil, plant and aerosol samples were found. Based on the simple binary Pb isotopic model using the mean 206Pb/207Pb ratios in TSP and in SSA, the approximate contributions of airborne Pb into plant leaves were 72.2% and 65.1%, respectively, suggesting that airborne Pb is the most important source for the Pb accumulation in leaves. So the combination of Pb isotope tracing and the simple binary Pb isotope model can assess the contribution of airborne Pb into plant leaves and may be of interest for risk assessment of the exposure to airborne Pb contamination. [Copyright &y& Elsevier]